1. Field of the Invention
The present invention relates to an improved drip chamber, and more particularly, to a drip chamber provided with a bubble trap filter that is designed to prevent the introduction of air bubbles into a fluid delivery system such as used for the administration of parenteral fluids to a patient or such as used for continuous flushing of a central arterial blood pressure monitoring system.
2. The Prior Art
The use of drip chambers as a component part of fluid delivery systems to administer parenteral fluids to a patient or such as used to continuously flush a central arterial blood pressure monitoring system has long been known in the art. Conventional drip chambers typically consist of a fluid resistor that is suspended and enclosed in a transparent chamber. The transparent chamber collects the fluid expelled from the fluid resistor, and by visually observing the rate at which drops of fluid fall from the fluid resistor the approximate rate of infusion into the patient may be determined, as well as verifying that fluid is in fact being infused into the patient.
In the past, a chronic problem has been the risk of introducing air bubbles into the fluid delivery system by reason of the drip chamber. Typically, this problem occurs in several ways. When the fluid delivery system is initially filled or when a large quantity of the infusion fluid must be rapidly washed through the delivery system, a high velocity jet of fluid is expelled from the fluid resistor in the drip chamber. The high velocity jet of fluid causes a venturi effect such that air is pulled with the high velocity jet of fluid and is injected into a fluid reservoir that collects at the bottom of the drip chamber. The air injected into the fluid reservoir forms numerous micro-bubbles which subsequently flow out of the drip chamber and into the tubing and catheter of the fluid delivery system. These air bubbles can become entrapped in the drip chamber and then later injected into the catheter delivery system.
Introduction of air bubbles into the fluid delivery system can be extremely hazardous. For example, it is well known that intravenous introduction of air bubbles may result in an embolism which may block a blood vessel. This can be extremely dangerous to a patient and in some cases way even result in death. Thus, the problem which is faced is how to eliminate the introduction of air bubbles into the tubing and catheter of the fluid delivery system.
Although various attempts to solve this problem have been made by those skilled in the art, to date there has not been devised an apparatus and method that has fully succeeded in achieving a saatisfactory solution to this problem.
For example, one typical attempt to solve the problem has been to place a fine mesh filter screen at the bottom of the drip chamber. This prior art technique has several significant drawbacks. For example, from time to time it may be necessary to rapidly inject fluid through the delivery system. When this occurs, as previously described, a high velocity jet of fluid is expelled through the fluid resistor which strikes the fluid reservoir contained in the drip chamber. The venturi effect and turbulence caused by the high velocity jet of fluid creates a large number of micro-bubbles that can be driven right through the screen that is placed at the bottom of the drip chamber.
Another serious drawback with the prior art approach to the solution of this problem is that when initially filling the fluid delivery system, large air bubbles are almost always trapped under the filter screen placed at the bottom of the drip chamber. The large air bubbles which are trapped beneath the filter screen are almost impossible to remove once the fluid delivery system has been filled. Thus, the existence of air bubbles trapped beneath the filter screen are a further factor which may cause concern on the part of medical technicians or other personnel using the fluid delivery system for the administration of parenteral fluids.
In summary, although the use of drip chambers as a component part of fluid delivery systems has long been recognized as an important way to verify the continuous infusion of fluid to a patient and to verify the approximate rate of infusion, there has not yet been devised an effective way of minimizing risk to the patient by eliminating the introduction of micro-bubbles into the fluid delivery system during rapid flushing of the system. Nor has there been devised an effective way to eliminate the air bubbles that are typically entrapped beneath the filter screen, such as currently used in most types of prior art drip chambers.